改造 2：在没有网络的情况下读取 JSON 时应用程序崩溃

Question

当用户没有互联网连接时尝试使用 Gson 和 Retrofit2 读取 json 信息时，我试图阻止我的应用程序崩溃。有任何想法吗？

我的代码：

分段

class ManuFragment : Fragment() {
    private lateinit var viewModel: ManuFragmentVM

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
        _binding = FragmentManuBinding.inflate(inflater, container, false)
        return binding.root
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        viewModel = ViewModelProvider(this).get(ManuFragmentVM::class.java)

        viewModel.apply {
            manufacturer.observe(requireActivity(), {loadRecyclerView(it)})
            setup()
        }
    }

查看模型

class ManuFragmentVM : ViewModel() {

    val manufacturer = MutableLiveData<List<Manufacturers>>()

    fun setup() {
        viewModelScope.launch(Dispatchers.Default) {
            manufacturer.postValue(CarsRepository().getAllManufacturers())
        }
    }

界面

interface ManufacturerApi {
    @GET("url.json")
    suspend fun fetchAllManufacturers(): List<Manufacturers>
}

存储库

class CarsRepository {

    private fun manufacturerRetrofit(): ManufacturerApi {
        return Retrofit.Builder()
            .baseUrl("https://website.com/")
            .addConverterFactory(GsonConverterFactory.create(GsonBuilder().create()))
            .build()
            .create(ManufacturerApi::class.java)
    }

    suspend fun getAllManufacturers(): List<Manufacturers> {
        return manufacturerRetrofit().fetchAllManufacturers()

    }

Answer 1

看起来您只需要将调用包装在 try-catch 中：

fun setup() {
    viewModelScope.launch(Dispatchers.IO) {
        try {
            manufacturer.postValue(CarsRepository().getAllManufacturers())
        } catch (ce: CancellationException) {
            throw ce // Needed for coroutine scope cancellation
        } catch (e: Exception) {
            // display error
        }
    }
}

另外，您应该使用 IO 调度程序显式运行 API 调用。你的其余代码看起来非常好。